The CC chemokine eotaxin/CCL11 has a selective profibrogenic effect on human lung fibroblasts

Background

Eotaxin/CCL11 plays an important role in asthma. It acts through the chemokine receptor CCR3 expressed on hematopoietic and nonhematopoietic cells in the lung.

Objective

To determine whether eotaxin/CCL11 modulates lung and bronchial fibroblast properties and thereby might contribute to airway remodeling.

Methods

CCR3 expression was characterized on a lung fibroblast line (MRC-5; flow cytometry, fluorescent microscopy, RT-PCR, and Northern blotting), on primary bronchial fibroblasts (flow cytometry), and on fibroblasts in human lung tissue (confocal laser microscopy). The effects of eotaxin/CCL11 on lung fibroblast migration (Boyden chamber), proliferation (tritiated thymidine incorporation), α-smooth muscle actin expression (ELISA), 3-dimensional collagen gel contraction (floating gel), pro-α1(I) collagen mRNA (Northern blotting), total collagen synthesis (tritiated proline incorporation), matrix metalloproteinase activity (gelatin zymography), and TGF-β₁ release (ELISA) were evaluated. The contribution of eotaxin/CCL11/CCR3 binding on lung fibroblasts was also investigated by neutralizing experiments.

Results

CCR3 is constitutively expressed in cultured lung and primary bronchial fibroblasts and colocalizes with specific surface markers for human fibroblasts in lung tissue. Eotaxin/CCL11 selectively modulates fibroblast activities by increasing their proliferation, matrix metalloproteinase 2 activity, and collagen synthesis but not their differentiation into myofibroblasts, contractility in collagen gel, or TGF-β₁ release. Eotaxin/CCL11 enhances migration of lung fibroblasts in response to nonspecific chemoattractants, and this effect is completely inhibited by anti-CCR3–neutralizing antibodies.

Conclusion

These data demonstrate that eotaxin/CCL11 has a direct and selective profibrogenic effect on lung and bronchial fibroblasts, providing a novel mechanism whereby eotaxin/CCL11 can participate in airway remodeling in asthma.

Key words: CC chemokine, eotaxin/CCL11, CCR3, fibroblast, myofibroblast, airway remodeling, asthma, α-smooth muscle actin

Abbreviations used: α-SMA, α-Smooth muscle actin, DMEM, Dulbecco's modified Eagle's medium, ECM, Extracellular matrix, HBF, Human bronchial fibroblast, HLF, Human lung fibroblast, MCP-1, Monocyte chemoattractant protein 1, MMP, Matrix metalloproteinase, PARC, Pulmonary and activation-regulated chemokine